An investigation into the relationship between the formation of thermal cracked components and PM reduction during diesel combustion using water emulsified fuel

Water-in-diesel emulsion fuel (W/O) operated in diesel engines, shows a significant reduction of particulate matter (PM). In this paper, PM reduction characteristics by thermal decomposition of W/O10 and W/O20 (10vol.% and 20vol.% of water in W/O respectively) are identified in diesel combustion atmosphere using a plug flow reactor with a co-flow diffusion burner. To analyze initial thermal decomposition at diesel diffusion combustion, the W/O fuels are thermally decomposed in the plug flow reactor first, then the thermally decomposed W/O fuels are introduced into a co-flow diffusion burner as fuel and PM are generated. In high temperature atmosphere without oxygen in the reactor, W/O10 and W/O20 are thermally decomposed and both of them almost produce light hydrocarbons (LHCs) higher than a diesel fuel, which means thermal decomposition before combustion are encouraged by the W/O. Excitation-emission matrix (EEM) method shows that polycyclic aromatic hydrocarbons (PAHs) are produced by both W/O fuels and diesel fuel during the thermal decomposition period but some W/O fuels oxidize a huge amount of PAHs in the later diffusion combustion. CO, CO₂ measurements after the combustion of the thermal decomposed substances in the diffusion burner via high temperature reactor reveal that diffusion combustion of W/O fuels contribute to Soluble Organic Fraction (SOF) and Solid reduction which leads to reduction of CO and increase of CO₂ respectively.